Fresh Pureed Pumpkin

To make pumpkin puree from a fresh pumpkin or jack o'lantern, remove the seeds and stem and cut the pumpkin into 2-4 inch chunks.
Cover them with water, and simmer for about 30 minutes until tender.  You can also steam the pumpkin  on a metal steamer or microwave until tender.
Cool slightly, but not completely and scrape from skin.  Puree in a blender in small batches.
(I often add water while it's blending to help it blend easier and then remove the water later.)
Use cheese cloth to squeeze out most of the water to make the puree less watery. 
Freeze in ziplock bags.  Or use immediately in cookies or pie.